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I was extending a circuit in my kitchen last week as part of a remodel and discovered something that had been under my nose the whole time I've lived here but I just paid enough attention to notice.

There are 5 multiwire branch circuits in my main panel (6 if you count the one I added), and only 1 of them (2 if you count the one I added) was handle-tied. Additionally, all of them have at least one leg (sometimes both) on double-stuff breakers.

Now, I know I need to fix this and it will involve moving at least 4 circuits around, probably more since I'll likely need to shift a few others just to get enough adjacent spaces.

My question is: When did handle tying a MWBC become code?

This house was built in 2010 in Riverside County CA, so the code in force would have been either the 2010 CA Electric Code (which adopts 2008 NEC) or the 2007 CA Electric Code which adopts 2005 NEC). Everything in that panel aside from the three 2-pole breakers at the top is original. They did put a couple AFCI breakers in for the bedrooms, so they were sort of on the ball. I don't know why thy used almost all tandems in a brand-new panel that only ended up just over half full. (Those 3 double poles at the top were added recently by me).

At least they got the poles on the right busses (hopefully on the first try) even though they aren't anywhere near adjacent. For example, the MWBC that serves 2 of the kitchen circuits is half on the bottom of the quad and half on a full-size single pole 3 spaces up. I've added colored tape patches to mark which circuits are MWBC.

enter image description here

Finally: when I fix this, since I will be moving circuits in this panel and possibly relocating 1 or 2 to my subpanel to make room, will I need to comply with the current code (2019 CEC/2017 NEC locally) and AFCI all the things? (If that's the case, it might become costly enough to justify seeing if I can find QO innards that fit this enclosure since I'll be replacing more than half the breakers anyway.)

Maybe I can find some ANSI grey tape to make it look original when I have to re-mark everything. :)

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    One doesn't tie MWBCs for code compliance. One ties them for safety! Contact your manufacturer to see if they offer handle-ties to tie adjacent throws on two tandems. You could just daisy chain them in one big stack! (well one stack for the 15s and another for the 20s). Noting the subpanel feeder on the 100A breaker, make sure that is #1 Al or #3 Cu. Many people falsely believe #2AL or #4Cu will suffice because they're reading the wrong table in NEC. The correct table is 310.15(B)(16) 75C column. Sep 23 at 16:51
  • @Harper-ReinstateMonica Very true. Now that I know they're MWBC, they're "safe" as long as I'm the only one working and know what to throw, but anyone in the future might get bit. Thanks for the tip on the double stack handle ties - I never thought of that and it could save a lot of breaker replacement.
    – Chris O
    Sep 23 at 16:54
  • @Harper-ReinstateMonica That sub feed is #2 Cu so no worries there.
    – Chris O
    Sep 23 at 16:56
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    Well 115A then! Max breaker 125A. Yeah, you may have noticed those breakers are QO guts in HOM clothing, which makes the spacing really funny. Swapping to a QO bus assembly is problematic here because of the meter being part of the enclosure, creating an entitlement nightmare. And QO breakers buy you a few more spaces but have less selection, so that may be constrictive in its own way. E.G. no 200A subfeed lugs or 200A branch breakers in QO. 20 spaces is just not realistic for a whole house, but meter+main+panel combos were not made much larger than that. Sep 23 at 17:01
  • @Harper-ReinstateMonica Funny you should mention 125A. I originally put the 100A in because it was available and I couldn't find the 125A in stock anywhere even though I sized the panel and feeder for it. Might upgrade it someday, but I will probably eventually add yet another sub somewhere else. These CSED enclosures are certainly too small. I can see them eventually becoming a de-facto MDF with subs serving the actual branch circuits.
    – Chris O
    Sep 23 at 17:32

4 Answers 4

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Seems like your potential code editions put you right on the cusp, as it was required starting in NEC 2008.

https://www.ecmweb.com/content/article/20890842/code-changes-2008

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  • Thanks - I was looking for that but didn't find the change log. There are so many other minor code violations in this house that I wasn't sure if it was even inspected in person or just rubber-stamped.
    – Chris O
    Sep 23 at 15:12
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I'm posting this down here because it fits more as an answer than an update to the question.

Turns out that while there is no official solution to handle-tie the outer pair of a quad/tandem breaker, Square D makes quad/tandem breakers that are factory handle-tied/common trip on both the inner and outer pairs. That would be a direct drop-in for my two 15A tandems as well as the 20A quad there, leaving me with only two circuits to rejigger.

These are they:

HOMT215215

enter image description here

HOMT220220

enter image description here

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Finally: when I fix this, since I will be moving circuits in this panel and possibly relocating 1 or 2 to my subpanel to make room, will I need to comply with the current code (2019 CEC/2017 NEC locally) and AFCI all the things? (If that's the case, it might become costly enough to justify seeing if I can find QO innards that fit this enclosure since I'll be replacing more than half the breakers anyway.)

I was worried about that myself recently with a heavy-up. My electrician assured me, and inspector approved, that existing circuits moved into a new panel did not need to be upgraded to AFCI and/or GFCI. .One receptacle needed to be replaced because the new panel (2 feet away from the old) took the physical space where it was, and for that the electrician put in a GFCI/tamper resistant, because he couldn't not do that when replacing a receptacle. However, other existing non-GFCI receptacles that were untouched at the receptacle end, but were in locations (unfinished basement or outside) that now require GFCI did not need to be upgraded, and no AFCI was needed even though most of the circuits, if new, would require it.

That being said:

  • Your jurisdiction may have different rules. They may require AFCI and/or GFCI when replacing a panel or when moving a circuit to another panel.
  • If the subpanel is in a truly different location - i.e., different room or more than a few feet away from the main panel - then circuits moved to it may be treated as "new" circuits even if no receptacles or other devices are actually added or changed.

The argument for requiring AFCI and/or GFCI to be added based on current code is that it will increase safety. The argument against it is that the added cost, which can be quite significant for AFCI and for double-pole GFCI (since only single-pole GFCI can be done inexpensively at the first receptacle) will discourage otherwise extremely beneficial safety upgrades. I went from 2 messed up (bad MWBC that I didn't know about until taking apart the fuse panel, and some other problems) fuse boxes and 1 small breaker panel, with sub-par house grounding and some other problems, to a beautiful 42-space CH panel with proper ground rod, generator interlock, etc. I had my reasons to upgrade anyway (most of my neighbors did many years ago) but an extra $ 500 - possibly quite a bit more - for AFCI breakers on most circuits, plus GFCI on a few, might have made me delay everything longer.

A call to either a local electrician or the local permitting office should be able to get definitive answers for your location.

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Hate to say it but you have a MUCH BIGGER PROBLEM on your hands: Those double stuff breakers that make up your MWBCs are ON THE SAME POLE, not opposite poles as is required.

So, what does that mean? It means that you can supply the circuit with TWICE the power the neutral is rated to carry back. This setup is NOT SAFE.

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    Doesn't look that way to me...per the tape markings they are set up as a quad would be.
    – Ecnerwal
    Sep 23 at 15:00
  • @Ecnerwal look at the breakers on the right side, clearly they have red and black wires going to the same double stuff breaker. Sep 23 at 15:03
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    That's the "blue-tape" MWBC red, and a different non-MWBC black. I've added colored tape patches to mark which circuits are MWBC.
    – Ecnerwal
    Sep 23 at 15:06
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    @GeorgeAnderson Yep, I was afraid of that at first, but I traced all the /3s and they are on opposite poles. Doesn't look that way at a glance though.
    – Chris O
    Sep 23 at 15:09
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    @ChrisO I suppose the best way to be sure is to put a voltmeter on the screws on the breakers (esp. the first one with blue tape) and if you get 240, it's good to go, if you get zero, uh ooh. Sep 23 at 15:22

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